1. Field of the Invention
The present invention relates to the structure of a lens barrel having lens frames that are driven to advance or withdraw via cam followers.
2. Description of the Related Art
Conventional lens barrels have lens frames that can be advanced or withdrawn. A mechanism made by combining a cam groove and a cam follower is generally utilized for driving the cylindrical lens frames to advance or withdraw them. The cam groove runs obliquely to an optical axis, and the cam follower is engaged with the cam groove so that the cam follower can slide freely.
A structure enabling the whole slider surface of the cam follower to slide on a cam slide surface has been adopted as the structure of the cam follower that engages with the cam groove and slides thereon.
Moreover, a structure having the straight shaft of the cam follower press-fitted into a locking hole in a lens frame and thus having the cam follower to fixed to the lens frame has been adopted as the structure of the cam follower to be fixed to the lens frame.
In a conventional lens barrel to which the cam and cam follower is adapted, lens frames are small-sized in compliance with a recent demand for a compact and lightweight camera. Moreover, the lens frames tend to be thinner.
The lens frames themselves are therefore likely to deform. As far as the foregoing conventional structure enabling the cam follower to slide is concerned, when force is applied to the cam follower, the lens frame may be deformed and the cam and cam follower may be disengaged from each other.
Moreover, since the dimension of the shaft of the cam follower press-fitted into the lens frame is very small, if force is applied to the cam follower, there arises a fear that the press-fitted shaft may come off or become unstable. Moreover, using an adhesive to fix the shaft is unfavorable in terms of a manufacturing process or product management. Adhesives are therefore hardly used.